Ceramics have been used in many fields since they have outstanding electric and magnetic characteristics in addition to their mechanical properties, such as, for example, heat resistance and abrasion resistance. Ceramics based on zirconia that have outstanding oxygen ion conductivity, heat resistance, corrosion resistance, toughness and chemical stability are used for solid electrolyte membranes of oxygen sensors and humidity sensor, as well as electrolyte sheets of solid oxide fuel cells.
To achieve a better performance of the electrolyte sheets for solid oxide fuel cells, it is desired to increase an effective area of cell reaction and to prevent gradual interface delamination of an electrode layer from the electrolyte sheet. For this purpose, a method of roughening a surface of an electrolyte sheet by blasting or etching has been proposed (Patent document 1). There have also been attempts to provide moderate roughness on the surface of the electrolyte sheets. Such attempts may include a method of roughening a green sheet, achieved by pressing a metallic mesh on the surface of the green sheet, which is a precursor of an electrolyte sheet, followed by firing the green sheet (Patent document 2); the method of roughening the green sheet may also achieved by sandwiching the green sheet with a roughening sheet, pressing and transferring the roughened surface of the roughening sheets to the green sheet, followed by firing the green sheet (Patent documents 3); and further, the method of roughening the green sheet may be achieved by casting a slurry containing an electrolyte material onto a roughened polymer film, followed by firing the green sheet (Patent documents 4). Furthermore, although its purpose is not for roughening the electrolyte sheet, but for increasing the effective area of the electrode by enhancing the surface area of the electrolyte sheet, a method has been disclosed in which dimples are formed on both sides of the electrolyte green sheet by a press die, followed by firing (Patent documents 5).
Though not related to the technology about the method of manufacturing the electrolyte sheet, there has also been a proposed method for manufacturing a setter used for firing. This method involves forming recessions or protrusions on a surface of a molded body by press molding using a tape or sheet, on which micro grains are adhered, or a resin sheet, whose surface is caved in by machining, followed by firing the molded body (Patent document 6); Further, the method of manufacturing the firing setter may involve press-forming the firing setter, using a metallic punch mold whose surface is formed to be uneven by machining, followed by firing the firing setter (Patent document 7).
The following is a list of cited prior arts and patent documents:
Patent Document 1: Japan Patent Application Publication H1-227362
Patent Document 2: Japan Patent Application Publication H9-55215
Patent Document 3: Japan Patent Application Publication 2007-313650
Patent Document 4: Japan Patent Application Publication 2002-42831
Patent Document 5: Japan Patent Application Publication H7-73887
Patent Document 6: Japan Patent Application Publication H9-278517
Patent Document 7: Japan Patent Application Publication H11-79852